Why Your Emails Go to Spam (and how to fix it)

You send an important email — a receipt, a password reset, a newsletter — and it vanishes into the spam folder. Nothing looks wrong; you're not a spammer. Yet the filter disagreed. Email deliverability is its own dark art, but the factors are knowable. Here's how filters decide, and how to win them over.

How spam filters decide

A spam filter scores every incoming email across several signals and routes it to inbox or junk based on the total. The big three buckets:

Factor	What it checks
Authentication	Did this really come from who it claims?
Reputation	Does this sender have a history of good mail?
Content & engagement	Does the message look spammy? Do people open it?

Get all three right and you land in the inbox; fail one badly and you're in junk — even with great content.

1. Authentication: prove it's really you

This is the foundation, and the most common cause of deliverability problems. Receiving servers want cryptographic proof your mail is legitimate, via SPF, DKIM and DMARC:

SPF — the servers allowed to send for your domain.
DKIM — a signature proving the message is genuinely yours.
DMARC — a policy telling receivers what to do with mail that fails.

If your authentication isn't set up, modern providers (Gmail, Outlook) increasingly send you straight to spam — or reject you outright. This is non-negotiable now. Set up all three before anything else.

2. Reputation: your sending history

Mailbox providers track your domain's and IP's reputation over time. It's hurt by:

High bounce rates (sending to dead addresses — see bounce types).
Spam complaints (people hitting "report spam").
Hitting spam traps (addresses that exist only to catch bad senders).
Landing on a blacklist.
Sudden volume spikes that look like a compromise.

Reputation is slow to build and fast to lose — and it follows you.

3. Content and engagement

Even authenticated, reputable mail can trip content filters:

Spam signal	Better approach
Spammy words ("FREE!!!", "ACT NOW")	Write like a human
Lots of links / one giant image	Balanced text and links
Misleading subject lines	Honest subjects
No unsubscribe link	Always include one
Low open rates	Send to people who want it

Engagement matters more than people realise: if recipients open and reply, providers learn your mail is wanted; if it's ignored or deleted unread, that signals "junk."

The deliverability checklist

Do	Why
Set up SPF, DKIM, DMARC	The authentication foundation
Keep lists clean (remove bounces)	Protects reputation
Honour unsubscribes immediately	Avoids complaints
Never buy email lists	Spam traps + complaints = disaster
Warm up new sending IPs/domains	Build reputation gradually
Monitor blacklists	Catch a listing fast

A monitoring connection

Deliverability fails silently — your mail just quietly stops arriving. Monitoring your email policy records (SPF/DKIM/DMARC) and your blacklist status turns an invisible problem into an alert, so you fix it before customers notice the missing emails.

The bottom line

	In one line
Authentication	SPF/DKIM/DMARC — now mandatory for the inbox.
Reputation	Built on low bounces, few complaints, clean lists.
Content	Write like a human; include unsubscribe; earn engagement.
Watch	Records and blacklists — failure is silent.

Landing in the inbox isn't luck — it's authentication, reputation, and respectful sending. Nail the SPF/DKIM/DMARC foundation, keep your lists and reputation clean, and your legitimate mail goes where it belongs.